Step 1: Plan:
Instead of testing every statement fully, find the one statement that is clearly false. Three of the four options contain B, so a false B settles the matter.
Step 2: Test statement B:
Untouchable castes are the Scheduled Castes in the constitution. The OBC list is made of other backward groups. So the claim that OBCs are mostly untouchable castes is false.
Step 3: Remove options with B:
Options 1, 3 and 4 all contain B. Only option 2 is left without B.
Step 4: Confirm the rest of option 2:
Option 2 says A, C and D. A holds because OBCs differ from region to region. C holds because the Kalelkar and Mandal commissions both came before 1990. D holds because southern states such as Tamil Nadu started the backward class movement earlier than the northern states.
Step 5: State the result:
All three statements in option 2 are true and it leaves out the false one.
Cross-check:
For a final check, count how many statements each option needs. Option 2 needs A, C and D to be true and B to be false. We found exactly that. If B were true, then the OBCs would be the same as the Scheduled Castes, and the country would not have needed a separate category and separate commissions for them. This shows once more why B cannot stand and why the other options fail.
Final Answer:
Option 2 is the answer.
\[\boxed{\text{A, C and D only}}\]